I want to prevent flooding of my (2-car) garage when it rains. I was thinking of installing a trench drain across the driveway, about a foot from the garage door, with a sump/catch basin at the end, and a sump pump to pump the water through a garden hose to the garden (about 2′ lift from the driveway surface, or 3-4′ from the bottom of the sump). I have a bunch of questions:
1. Is this something a do-it-yourselfer can do along with one or two hired laborers?
2. Preformed steel drain/preformed poly-concrete drain/poured-in-place or “something else”? Why? Cost? Ease of installation? Durability/reliability/load capacity?
3. The entire back yard is concrete, except for the area where we removed some to make the garden. I don’t want to mess with breaking up an additional 30′ of concrete to lay drainpipe from the catch basin to the garden — hence the garden hose. They do make sump pumps with hose adaptors, but an Internet search doesn’t turn up any catchbasin grates with a hole large enough to pass the hose out. Suggestions? Should I pass the hose out through the outlet knockout in the catchbasin, and up to the surface (and block out a space for it in the concrete pour)? Attach a short drainpipe up to the surface from the catchbasin outlet, and pass the hose through that?
4. Will one of those big push-type concrete cutters rented from Home Depot work for cutting the driveway concrete? Will it work if the concrete has rebar in it?
5. Is this type of work likely to require a building permit?
6. This is in the San Francisco Bay area (Oakland/Berkeley border in the flats). The driveway has minimal slope down from the street, but there are no storm sewers, and some parts of the street flood in sustained heavy rains. Supposedly not on our block, but this is my first winter here, so I don’t really know how bad it gets. I understand that flooding of garages is common — don’t know about back yards. Anyway, what capacity of sump pump would you recommend?
Thanks for any insights or tips.
Rebeccah
Replies
Cutting concrete and ptting in a grate doesn't sound very DIY friendly to me. The concrete needs to have a lip for the grate to sit on - You can't just cut it off.
Running a sump pump through a garden hose also sounds like a bad idea. They're made to pump high volumes of water at low pressure. Restricting it down to garden hoe size would probably burn up the pump. It would probably work O.K with a 2" PVC or something similar, though.
And finally, runniong a bunch of water to your garden may work well when it's been dry and you get a light rain. But what about one of those days when you get 3" of rain after the ground is already saturated?
I'd suggest considering some sort of water storage, such as barrells. Or put a "T" in the pipe with a couple of valves so you can divert the water elsewhere when it's too wet.
Sex and golf are the two things you can enjoy even if you're not good at them." [Kevin Costner, Tin Cup]
Thanks for the quick response, Boss.
"Cutting concrete and ptting in a grate doesn't sound very DIY friendly to me. The concrete needs to have a lip for the grate to sit on - You can't just cut it off. "
Yeah, I was thinking about that -- the preformed drain systems take care of the lip issue, which was one reason I was thinking about using them.
"Running a sump pump through a garden hose also sounds like a bad idea. They're made to pump high volumes of water at low pressure. Restricting it down to garden hoe size would probably burn up the pump. It would probably work O.K with a 2" PVC or something similar, though. "
Good point. The outlets on the preformed systems are typically 4" or 6" in diameter. Then I guess the question would be whether I can run that above ground (2 90-degree bends).
"And finally, runniong a bunch of water to your garden may work well when it's been dry and you get a light rain. But what about one of those days when you get 3" of rain after the ground is already saturated? "
On those days, I'm sunk no matter what. The property is a bit less than 4000 sq ft. The garden is on the opposite side of the back yard from the garage, is higher than the driveway (everything is higher than the driveway)-- and is the only point, other than the front lawn, that is not encased in concrete already. The driveway is nearly flush to the house. If I pump the water to the front, I have to go up the driveway past the house and front sidewalk (to get away from the foundation) and then turn and cross all the way to the other side of the front yard past another sidewalk -- otherwise, the water will roll right back down the driveway again.
"I'd suggest considering some sort of water storage, such as barrells. Or put a "T" in the pipe with a couple of valves so you can divert the water elsewhere when it's too wet."
At least, there is a concrete buffer between the garden and the garage, between the garden and the back fence, and between the garden and the house. So even if that soil becomes saturated, the water is not going to run off and into something critical -- and I may yet build a low wall around the garden, allowing it to act as a water storage of sorts, if necessary.
The long term solution is to tear down the garage and build a new outbuilding (it's not used to park cars anyway) on a foundation, with or without regrading the driveway to slope *up* to the outbuilding. Don't know whether or not I'd be able to get a permit to regrade the driveway because of the drainage effect on the next door neighbor, though.
In the meantime, I just want to do something relatively inexpensive to prevent flooding due to surface water runoff, so my fiance can use the space for his art.
Thanks again,
Rebeccah
The first thing that I would go would be check with the immediate neighbors on each side to see how bad the problem is. If it is run off from the road you might want to put up a some hump of asphalt to divert it and keep if off the drive. Where i am those are common, but probably not the whole solution.
You will want to cut the driveway oversize for the prefab tench drain system. It will get filled in with the concrete needed to set the drain.
Yes you will need an larger collection box to hold the pump.
There are all kinds available.
Here is a company that makes trench drains and they also make undergrond enclousers that could be used.
http://www.strongwell.com/PolymerConcrete/Quazite/5BoxStyles.HTM
But a section of concrete culvert set vertically or a basement sump pump can would work.
The barrier idea is another one I've been thinking of, and I haven't completely ruled it out. The problems are:
1. There's no place to divert the water to -- the back yard is 2' higher than the driveway. So I'd still need a sump pump to lift the water.
2. The garage door is hinged near the top, not a roll-up. So the barrier would have to be set back from the door to allow it to open. If I set it back on the driveway, then there is still the rain that falls between the barrier and the door to cope with (obviously, a smaller problem than all of the rain in the driveway). If I put the barrier just inside the garage door, then one would have to step over it to get inside (the side door is already blocked by concrete put in the back yard by the previous owner), and one couldn't roll anything in or out.
So, I'm still thinking.
Rebeccah
1. Is this something a do-it-yourselfer can do Yes.
4. Will one of those big push-type concrete cutters rented from Home Depot Yes. They also rent cutting saws not on wheels, looks like a chain saw body & handle with a very large circular blade on the business end. Here they rent for $50/day and will cut about 5" deep, which shopuld be enough for your driveway.
Anyway, what capacity of sump pump would you recommend? Need to do a little ciphering. Measure your driveway ... 16 ft wide x 30 ft long = 480 sf. What is a heavy rain in your area? One inch per hour? That's 69,120 cu inches per hour. 231 cu-in/gal = 299 gallons/hour heading for your garage. The pump needs to handle at least 5 gallons per minute.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
Edited 9/22/2004 9:48 am ET by Ed Hilton
Thanks, Ed.
Have you ever done a project like this? Are you familiar with any of the pre-formed system? I'm wondering if they are worth the extra cost. It seems I can easily spend $400-500 on shipping alone.
"Need to do a little ciphering. Measure your driveway ... 16 ft wide x 30 ft long = 480 sf. What is a heavy rain in your area? One inch per hour? That's 69,120 cu inches per hour. 231 cu-in/gal = 299 gallons/hour heading for your garage. The pump needs to handle at least 5 gallons per minute."
To my surprise, the driveway is only 16' wide, just as you guessed (I thought it was more like 20'). It's 100' long. A web search for rainfall rates in Oakland turned up a nice little web site by a local meteorologist analyzing some flooding that occurred in the Bay area last February. He lives in Oakland and got about 1" per hr of rain at the peak of the storm, but says that is very unusual for the lowland areas of the Bay region. His graph shows mostly less than 1/4" per hour through the bulk of the storm, with just one hour of intense rain. I remember that storm, and it was indeed unusual. In fact, it was the storm that produced the street flooding that I alluded to earlier. But I don't think 1/2" per hour would be at all rare. So, let's see:
1600sf x 144 = 160000 + 64000 + 6400 =224000 + 6400 = 230400 sq in.
230400 sq. in x 1/2 = 115,200 cu in/hr., or about twice your estimate. So I should be looking for a 10 GPM pump minimum.
Good to hear from you again, it's been a while.
10 GPM is not a very big sump pump, it might, in fact, have a garden hose attachment for the discharge <g>.
i second the notion of checking with the neighbors on how much rain to expect, and whether it's the rain from the house, or runoff from the street that is the biggest problem. It may be that just catching the runoff from your own roof (with a downspout) barrel might be enough to control water flow towards the garage.
If, on the other hand, you are at the bottom third of an SF hill, you might be looking at trying to hold back the red sea--which would want a different sort of solution.
If you are going to have the concrete saw out anyway, it might be easier to cut into the concrete over the back yard (which is less likely to be either thick or filled with rebar), and trench in a drain down to the foot of the driveway. Since the backyard is essentially paved, the trench would not need to be terribly deep, it just needs to have a decent pitch. The trench could then be covered with a good quality decoative gravel, which would also help direct runoff, too.
Hope that helps, for only being 2¢ worth.Occupational hazard of my occupation not being around (sorry Bubba)
You'll never get 10GPM out of a garden hose. I think I get about 5GPM out of my garden hose from town water pressure.
I have a small pump that has a garden hose attachment. with 50' of garden hose it does about 2 GPM.
MERC
Is there anyway you could draw a quick scetch of your lot with the house and drive on it and show some elevations and post it. The sump seems like the best Idea but the question is were do you pump it to.
Edited 9/22/2004 1:25 pm ET by Jack -O-Trades
I'd love to post a sketch, but I have no idea a) how to post attachments, or b) what an appropriate tool would be to create the sketch.
I guess if someone could clue me in on how to do the former (and what file formats are appropriate), I could figure out how to do the latter. I don't have a scanner. :(
Thanks all,
Rebeccah
OK, here's the first sketch -- a side elevation.
I'm at work, so I won't be able to work on another sketch for a while.
What type of soil is naturally found under this concrete? By where you put the garden?
I understand one's need for a garden, but if you've got that California clay, you may be causing another problem.
When I bought in S. Cal, the geologist told me the biggest issue I would have would be from water getting into the expansive clay and causing the concrete to crack.
By cutting out a section of concrete for a garden, you're introducing a source of water for a possible concrete problem. Furthermore, that type of soil and elevation you describe wouldn't allow adequate soil drainage for a successful garden.
The previous owner may have had all of that cement for a reason...
"What type of soil is naturally found under this concrete? By where you put the garden?"
"I understand one's need for a garden, but if you've got that California clay, you may be causing another problem."
It's actually a nice loam. The garden is the back 1/3 of the back yard, up to about 6 feet from the garage.
"When I bought in S. Cal, the geologist told me the biggest issue I would have would be from water getting into the expansive clay and causing the concrete to crack."
Northern CA and Southern CA are quite different, geologically. Northern CA itself is geologically very diverse. I'm in a "soil liquefaction zone" from an earthquake perspective. The soil is friable and the water table is high. The concrete is at risk from the mobile soil, but clay doesn't seem to be the issue.
Besides, the concrete was already cracking when I bought the house, due to extremely poor installation technique.
I'm no expert by any means, but whoever put in the concrete clearly didn't know wtf they were doing. It was evidently done in two separate pours, probably at least a year apart. The bottom pour had what I guess are expansion joints -- wood planks a foot in from the current periphery and at 1/3 intervals from front to back. The top pour has no joints , was not screed, is not level, has areas where it looks like someone went and piled a little more on to fill a depression, and is splashed all over the fence and the siding on the non-garage side of the house. And it buries the bottom of the cellar door frame and abuts the side of the garage. As I mentioned, it was already cracking before we moved in June 30. It's a mess, and the whole thing really needs to be redone right, but not until I've figured out an overall site drainage plan and landscaping plan and a budget. (The kitchen also needs a major re-do and there is termite work to be done under the front porch, as well as tearing down and rebuilding the garage.)
"By cutting out a section of concrete for a garden, you're introducing a source of water for a possible concrete problem. Furthermore, that type of soil and elevation you describe wouldn't allow adequate soil drainage for a successful garden."
Other lots on our block have very successful gardens, but it's not top priority right now anyway. Time and trial and error will overcome any gardening obstacles.
"The previous owner may have had all of that cement for a reason..."
No argument here. The putative reason: "His child has allergies" (per the seller's realtor). "He doesn't like grass" (per the neighbor two doors down). I don't buy it. But I did buy the house, so I'm stuck with it. :)
I think the concrete was put down because of drainage problems, but I don't think the way it was done will solve the problems that motivated its placement.
Rebeccah
And did you say the ground also slopes up behind the garage? Does that mean your house and garage is in a shallow sort of pit?
The back of the garage is about 1' from the property line. I'm not sure what's on the other side of the fence.
The next door neighbor's lot is properly graded (from her point of view) on my side -- it is sloped away from her house, but onto my driveway, which is right on the lot line. It's about 6" of drop over about 3 feet. Her back yard is maybe 1-2" higher than my driveway.
The garage is in a shallow hole. The house's floor is above street level. My sketch is not to scale.
Rebeccah
You did good with both the sketch and the attachment.
You definitely need to find someplace to send the water. You're just not allowed to give it to the neighbors anymore <g>.Occupational hazard of my occupation not being around (sorry Bubba)
Here's a sketch of the lot. Again, it's not to scale.
Oops. I tried to edit the image after posting it, and it let me delete it, but wouldn't let me add it back. Here it is again.
I was in lowes this morning and happened down the aisle with the pumps. Saw a submersible that advertised 25 gpm or 25 ft head through a garden hose. I forget if you said how much lift you need, but maybe this would work. Even if the gpm falls short of your calculations, it would certainly help.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
Does the front yard slope back, or towards the street at all?
This could be a tad exciting. You don't generally want a pipe bigger than 2" (I.D.) through a 6" curb (assuming that the City will permit that at all). That's a long uphil run to boot.
How attached are you to the garage <g>? It almost looks as if a crawl-space rainwater cistern with a shop/storage above might be the answer (and a carport in front of that). What to do with all that water might get a tad problematic, your gardern might not need that much watering.
Hmm, maybe what you need is a big backyard water feature <g>Occupational hazard of my occupation not being around (sorry Bubba)
"Does the front yard slope back, or towards the street at all?"
The front yard is basically level. It might slope back toward the house verrry slightly.
"This could be a tad exciting. You don't generally want a pipe bigger than 2" (I.D.) through a 6" curb (assuming that the City will permit that at all). That's a long uphil run to boot."
The hill's not that steep, but it is a long run.
"How attached are you to the garage <g>? "
In the short run, I'm attached to the garage for storage and a place for my fiance to do messy work (he's an artist). In the long run, maybe as soon as next year, it's got to go. The mud sills are rotting, the back wall has a couple of studs that have the bottom halves sawed off (I presume also because of rot, but I don't know), the whole thing is racked a few degrees, it has no earthquake bracing (which you could guess from the fact that it's racked), and it will need a new roof soon. It's in better shape than most of the garages around, though. :)
Money's going to be an issue, though.
"It almost looks as if a crawl-space rainwater cistern with a shop/storage above might be the answer (and a carport in front of that). "
What all is involved in creating a rainwater cistern? And what kind of order of magnitude are we talking, cost-wise? Wouldn't I have to worry about breeding mosquitoes if I put in a cistern?
I was thinking about the carport-in-front-of-a-workshop idea when I was first looking at the property. It's a maybe. But if I put it next to the house, it will block light into the dining room and kitchen; if I put it in front of the garage location, and behind the house, we lose a nice open, sunny barbecue patio. On the other hand, if we redo the back yard crappola concrete job at the same time, we can make a nicer one. :)
"What to do with all that water might get a tad problematic, your gardern might not need that much watering.
Hmm, maybe what you need is a big backyard water feature <g>"
You grin, but my fiance want to do that anyway. He wants to sculpt a windmill type statue and put it in a pond. (Note: He'll never actually do it, at least not in the near term. It requires a kind of sustained attention that I don't think he is willing to devote right now.)
Hmm, maybe what you need is a big backyard water feature <g>"
You grin, but my fiance want to do that anyway. He wants to sculpt a windmill type statue and put it in a pond. (Note: He'll never actually do it, at least not in the near term. It requires a kind of sustained attention that I don't think he is willing to devote right now.)
I can't take full credit for the idea--there's an episode of Ground Force, where a Submariner's front yard is made into a water feature which defined the planting boundries. The effect was rather of a shallow pool with planting "islands" in it. The reality was that there was actually ony a small amount of water.
So, you could have the bbq area, and it could have a 12" wide border of water with bridges to other areas. You'd need a goodly amount of pond liner. You already need a sump, so a recirculating pump would not be that big an addition. (Easy for me to say)Occupational hazard of my occupation not being around (sorry Bubba)
What all is involved in creating a rainwater cistern?
As much as the budget allows (and Bay area prices could make that scarier besides).
Down Austin way (where water prices and lack of rainfall combine), it's not too bad. You build a crawlspace/kneewakk around 500 or 700 gallaon bladders, and deck over that. The two hassles around Austin are finding enough soil depth (so as to not have to cut into solid rock), and making up a flexible connection to the downspout's leader to the bladder filler. It's also earthquake Zone 0, too.
The concept is not too complicated. You need a low wall and a slab which can be waterproofed to hold water. It's pool construction meets basement wall construction. A concrete plank deck to finish makes a clean detail.
Clean, neat, etc., just probably not cheap or easy near the Bay.Occupational hazard of my occupation not being around (sorry Bubba)
"Down Austin way (where water prices and lack of rainfall combine), it's not too bad. You build a crawlspace/kneewakk around 500 or 700 gallaon bladders, and deck over that. "
There's no shortage of water here in the winter. What do you do when the bladders are full?
What's the advantage of this over, say, building the new garage over a crawlspace and letting the water go into the ground under the crawlspace? I guess it's a dumb question -- moisture in the air over the crawl space, in the walls, etc. -- but this is a garage, not a house, and can be left open to air out. And I *don't* need the water for anything.
I guess the other question is how hard is it/how much more expensive is it to build a non-slab-on-grade floor that can withstand automobile loads, should one choose to park them inside after all (compared to a standard slab, or compared to a standard house-type floor)?
For that matter, how expensive would it be to simply regrade the driveway to slope down toward the street? It would require raising the driveway end probably 4-6 feet. The driveway is 100' long, and the garage is whatever the standard depth is for a 2-car garage.
Rebeccah
You'll need some advice with more Bay area experience, I'm thinking. For rebuilding the driveway, I know any top=of-the-head numbers will be off by at least a third. There will be structural & seismic concerns that I could miss, too.
Building a floor spanning a crawlspace to hold cars is not that tought, it's more of an engineering problem (that, and chosing a POL-resistant floor surface). We had a Billups Lube oil storage building in town that was entirely built with structural lumber, including the floor. If that floor could stand forklift traffic, a car is no problem. Economic, that's a different story.
Wish I could offer more actual help.Occupational hazard of my occupation not being around (sorry Bubba)
I have a crazy idea (not unusual for me)--this might be best for the future: when you rebuild or remove the garage, put a cistern in where the garage sat (big underground tank). Then just let the water fill it, since it seems to want to anyway. Then pump from there or use gravity to water the garden. Could build a studio or whatever over the cistern if wanted.
So here's the latest update.
I just discovered White Cap (which I understand was bought by Home Depot a few months ago), so I got a source for the preformed polymer-concrete drain system -- a LOT cheaper than ordering it from the Internet and having to pay shipping. We rented a concrete cutter, and the concrete cutting was very easy. My fiance has now removed the concrete and dug the trench. We're going to pour the sump basin in place using sheet metal for a form, and I got an 18" sewage pit cover to put over it.
I have a couple of additional questions, but my fiance just got here to pick me up from work, so now I have to go. I'll post again later.
Rebeccah
Here's a sketch of the planned drain (garage is at the top; on the left is a a brick border and a fence to the neighbor's yard; on the right, a buried 60A electrical feed to the garage and a step up to the concrete-encased back yard). 6" of concrete on either side of the drain system; 4" minimum distance from the sump pit to the edge of the concrete pour. We'll probably put rebar in the concrete around the sump pit. We'll make the form for the sump pit out of aluminum sheet-metal. We're suspending the preformed drain pieces from 2x4's spanning the trench -- seems to me to be easier to adjust that having to pound rebar into the trench bottom to support the installation clamps.
It rained this morning, and I can see there is still a small puddle of water in front of the corner of the garage near the sump pit, but we can't really get any closer because of clearance for the saw and a general desire not to cut the electrical conduit. We'll probably build up the concrete a bit over there and slope it down towards the sump pit.
Questions:
1. My fiance wants to layer the concrete with course aggregate culled from the concrete he removed, to make it stronger. I know using course aggregate *in* the concrete makes it stronger, but I never heard of layering it during the pour. Does this idea make sense to you? He's going to be hiring laborers and mixing the concrete with a shovel (no readi-mix truck, no power mixer -- I know, it's a lot of concrete to mix by hand).
2. The installation instructions for the trench drain system say to put an expansion joint on either side of it. The attached sketch shows where I plan to put the 1/2" expansion joint strips. The existing concrete has control joints about every 3 1/2' or so, and they do seem to work. Does this look like a reasonable placement for the expansion joints?
3. Anything else we should know before we pour?
Thanks,
Rebeccah
FYII'm moving about 1500 GPH thru a 1.5 in pipe about 30 ft with a 14 ft head.pond/watrfall_____________________________
bobl Volo, non valeo
What does "a 14 ft head" mean?
the water is being lifted 14 feet.from the pump to the height the water is being lifted is 14 feet.think pumps are advertized at zero feet, no lift. they max out at some lift where you will get no flow. each pump differentas lift height rises then flow rate goes downbtw, think that my pump came with a 1 1/4 outlet and inlet, i changed the outlet to 1 1/2 inches.also, u can get flexible pvc at watergarden stores, but it is not cheap. also there is the piping used for sprinkler systems_____________________________
bobl Volo, non valeo
Thanks.Oh, yes, I've been hunting around for the corrugated pipe and found some, and a sump pump. I've only got 3-4' of head and 20-30' of lateral distance to transport the water, so a 1/3HP Wayne pump should be satisfactory. It has a 1 1/2" discharge, and I actually need a reducer to get the check valve attached. Go figger.At this stage of the game, I'm just considering the issues surrounding the concrete pour. Course aggregate layered in (as my fiance suggests) vs mixed in (which I've heard of)? I guess if he makes thin layers, they'll probably mix a certain amount just from pouring and spreading the concrete around the channel pieces.And the expansion joints. It took me a while to come up with what to do about the channel overhanging into the deep part of the hole for the sump wall, because the joint should naturally be at a break in the channel. I think what I have pictured in my last post makes sense, but I was just looking for some confirmation.Also, do you know if you're supposed to put the sealant on the ends of the channel pieces before putting them together, or caulk the outside or the inside after putting them together? One end has a male bevel and the other a female, but they're not anything like a snap-fit.Thanks,Rebeccah
Ta-daahhh!
We did it.
Here are photos of the trench, the modular drain (by ACO), the first concrete pour, and the final result. It's working great! It rained all night and this morning, and the garage is dry. The garden is pretty soggy, as expected.
My fiance hired two laborers to help him pour the concrete, one of whom had prior experience doing foundation work and knew the tricks of the trade. Someone kicked one of the drain pieces so it's out of alignment by about 1/4", and my fiance didn't put the expansion joint strips exactly where I had wanted around the sump pit, but overall I think it came out remarkably well.